Segmented Insert
Gradient Coil for Bilateral Knee Imaging

MRI
of the knee can benefit from high spatial resolution and short echo times for
both proton and sodium-23 imaging of cartilage. With higher gradient strength
and slew rate, the insert gradient coils can attain shorter echo times and
higher spatial and temporal resolution than the body gradients. Prior flat
gradient system designs have relatively smaller HGVs, which are not quite
wide enough for bilateral knee imaging. To image both knees simultaneously,
we have developed a segmented two-region insert gradient system which has two
wide HGVs, one for each knee, along the x-axis. This was achieved by adding
an extra vertical winding in the middle of the x-gradient to create high
gradient strength, and by using superelliptical geometry, which enlarges the
HGV dramatically by spreading wire patterns around both knees.